The present invention is directed to recording papers suitable for use in electrostatographic printing processes. More specifically, the present invention is directed to coated papers that, when used in electrostatographic recording processes, including electrography, electrophotography, xerography, ionography, and the like, enable generation of glossy prints that simulate those obtained with silver halide technology. One embodiment of the present invention is directed to a recording paper which comprises (a) a cellulosic base sheet having a first surface and a second surface opposite the first surface, said base sheet having a dielectric constant of at least about 1.5 under conditions of about 50 percent relative humidity and at about 23xc2x0 C., said base sheet having a dielectric constant of no more than about 10 under conditions of about 50 percent relative humidity and at about 23xc2x0 C., said base sheet having, under conditions of about 50 percent relative humidity and at about 23xc2x0 C., a surface resistivity of at least about 1xc3x97107 ohms per square, said base sheet having, under conditions of about 50 percent relative humidity and at about 23xc2x0 C., a surface resistivity of no more than about 1xc3x971013 ohms per square; (b) on the first surface of the base sheet an image receiving coating comprising a monomeric or polymeric material, said image receiving coating having a glass transition temperature of at least about 55xc2x0 C., said image receiving coating having a surface resistivity that is within about 10 percent of the surface resistivity of the base sheet, said image receiving coating having a gloss value of at least about 50 GU; and (c) on the second surface of the base sheet a back coating comprising a monomeric or polymeric material, said back coating having a surface resistivity that is within about 10 percent of the surface resistivity of the base sheet.
Recording substrates for electrostatic printing processes are known. For example, U.S. Pat. No. 5,663,029 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a process for generating images which comprises (1) generating an electrostatic latent image on an imaging member in an imaging apparatus; (2) developing the latent image; and (3) transferring the developed image to a recording sheet which comprises (a) a substrate; (b) a coating on the substrate which comprises (1) a binder selected from the group consisting of (A) polyesters; (B) polyvinyl acetals; (C) vinyl alcohol-vinyl acetal copolymers; (D) polycarbonates; and (E) mixtures thereof; and (2) an additive having a melting point of more than about 65xc2x0 C. and a boiling point of more than about 150xc2x0 C. and selected from the group consisting of (A) furan compounds; (B) pyrone and pyran compounds; (C) dioxane compounds; (D) aromatic anhydrides; (E) aromatic esters; (F) alkoxy compounds; (G) methylene dioxy compounds; (H) quinone compounds; and (I) mixtures thereof; (c) an optional filler; (d) an optional antistatic agent; and (e) an optional biocide.
U.S. Pat. No. 5,663,030 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a process for generating images which comprises (1) generating an electrostatic latent image on an imaging member in an imaging apparatus; (2) developing the latent image; and (3) transferring the developed image to a recording sheet which comprises (a) a substrate; (b) a coating on the substrate which comprises (i) a polymeric binder selected from the group consisting of (A) copolymers of styrene and at least one other monomer; (B) copolymers of acrylic monomers and at least one other monomer; and (C) mixtures thereof; and (ii) an additive having a melting point of more than about 65xc2x0 C. and a boiling point of more than about 150xc2x0 C. and selected from the group consisting of (A) norbornane compounds; (B) phenyl compounds; and (C) mixtures thereof; (c) an optional filler; (d) an optional antistatic agent; and (e) an optional biocide. In a preferred embodiment, the latent image is developed with a liquid developer.
U.S. Pat. No. 6,177,222 (McAneney et al.), the disclosure of which is totally incorporated herein by reference, discloses a process which comprises forming an image on a substrate, and developing the image with toner, and wherein the substrate contains a coating of a polyester and there is enabled images of high uniform gloss.
While known compositions and processes are suitable for their intended purposes, a need remains for improved papers for use with electrostatic imaging processes. In addition, a need remains for papers that, when used in electrostatic imaging processes, generate images with uniform high gloss. Further, a need remains for papers that, when used in electrostatic imaging processes, generate images that approximate the look and feel of images printed on conventional high gloss silver halide photographic paper. Additionally, a need remains for papers that, when used in electrostatic imaging processes, enable high toner transfer efficiency in various different transfer systems, such as constant current roller systems, constant voltage roller systems, corona systems, and the like. There is also a need for coated high gloss papers that, when used in electrostatic imaging processes, enable high density toner transfer. In addition, there is a need for coated high gloss papers that, when used in electrostatic imaging processes, exhibit reduced or no dielectric breakdown in low toner density areas. Further, there is a need for coated high gloss papers that, when used in electrostatic imaging processes, enable generation of images wherein the gloss of the imaged areas approximately matches the gloss of unimaged areas. Additionally, there is a need for coated high gloss papers that, when used in electrostatic imaging processes, are compatible with a number of different fusing systems, including both those employing fuser oils and those employing no fuser oils. A need also remains for coated high gloss papers that can be used in electrostatic imaging processes to generate images with electrostatic dry toners. In addition, a need remains for coated high gloss papers that can be used in electrostatic imaging processes to generate images with electrostatic liquid developers. Further, a need remains for coated high gloss papers that, when used in electrostatic imaging processes, exhibit desirably low paper curl. Additionally, a need remains for coated high gloss papers that, when used in electrostatic imaging processes, exhibit good dimensional stability. There is also a need for coated high gloss papers that have relatively constant dielectric properties with respect to humidity to enable wide toner/paper transfer latitude across various environments. In addition, there is a need for coated high gloss papers wherein the coatings enable the paper thus coated to maintain relatively stable moisture content values across a wide range of relative humidity conditions. Further, there is a need for coated high gloss papers wherein the coatings enable the paper thus coated to maintain relatively heat capacity values across a wide range of relative humidity conditions. Additionally, there is a need for coated high gloss papers that have predictable fusing characteristics across a wide range of relative humidity conditions. A need also remains for coated high gloss papers that have predictable gloss characteristics across a wide range of relative humidity conditions. In addition, a need remains for coated high gloss papers that exhibit reduced curling when used in imaging processes. Further, a need remains for coated high gloss papers that enable toner transfer via control of the electrical properties of the paper. Additionally, a need remains for coated high gloss papers that exhibit desirable degrees of stiffness.
The present invention is directed to a recording paper which comprises (a) a cellulosic base sheet having a first surface and a second surface opposite the first surface, said base sheet having a dielectric constant of at least about 1.5 under conditions of about 50 percent relative humidity and at about 23xc2x0 C., said base sheet having a dielectric constant of no more than about 10 under conditions of about 50 percent relative humidity and at about 23xc2x0 C., said base sheet having, under conditions of about 50 percent relative humidity and at about 23xc2x0 C., a surface resistivity of at least about 1xc3x97107 ohms per square, said base sheet having, under conditions of about 50 percent relative humidity and at about 23xc2x0 C., a surface resistivity of no more than about 1xc3x971013 ohms per square; (b) on the first surface of the base sheet an image receiving coating comprising a monomeric or polymeric material, said image receiving coating having a glass transition temperature of at least about 55xc2x0 C., said image receiving coating having a surface resistivity that is within about 10 percent of the surface resistivity of the base sheet, said image receiving coating having a gloss value of at least about 50 GU; and (c) on the second surface of the base sheet a back coating comprising a monomeric or polymeric material, said back coating having a surface resistivity that is within about 10 percent of the surface resistivity of the base sheet.